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Natural Science - Year II

Unit 54: Rutherford and Atomic Structure

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Science Weblecture for Unit 54

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Science Lecture for Unit 54: The Bohr Atom

For Class


More Atom Basics

Read about the development of the empty atom concept and the Bohr atom. [2 moderate web pages.] Don't focus on the mathematics, but try to understand the key relationships involved: what physical entities are being described? For example, 1/2mv2 is kinetic energy.

  • Rutherford discovered that radioactivity decreases geometrically as time passes. How is a geometric progression different from an arithmetic progression?
  • How do we explain the very small deflection most alpha particles experience passing near the nucleus?
  • Why does direct deflection back from the foil disprove the "plum pudding" model?
  • What is a hyperbolic path? How does it differ from a parabolic path or a circular path?
  • Why was large angle scattering important in determining the size of the nucleus?
  • What did Rutherford originally think the α particle was made of?
  • Can an electron have an orbit of any radius when it is part of an atom? Why is this a problem for classical mechanics?
  • How is the kinetic energy of an electron related to frequency? What does this frequency measure?
  • What did Richard Whiddington's experiments with x-rays show about atoms?
  • What is Balmer's formula? What does it predict? What is "n" in the formula?
  • How are the radius and speed of the orbit of an electron proportional to "n"?

A more graphic treatment of the different parts of the atom is presented at the Trium Safety Group site, by Noel Griffin.
[7 really short web pages with graphics: read them all:

  • Atomic structure
  • The Nucleus and Electrons
  • Atomic Number
  • Atomic Mass
  • Electron Orbits
  • The size of the electron
  • Chemical symbols

  • Why is a fixed structure hard to describe for the atom?
  • How many types of atoms occur "naturally"? How are "unnatural" atoms produced?
  • Why is the mass of the electron usually ignored when determining the mass of an atom?
  • What is an electron shell?
  • What parts of the atom are affected by chemical reactions (such as the recombination of sugar molecules into carbon dioxide and water)?
  • Roughly how much larger than the nucleus is the atom with its electron shell?

Study/Discussion Questions

Further Study On your Own (Optional)